Stabilization of vinyl resin foam systems

ABSTRACT

VINYL RESIN FOAM PRODUCTS HAVING DESIRALE CHARACTERISTICS INCLUDING FINE UNIFORM CELLULAR STRUCTURE AND LOW DENSITY ARE PREPARED WITH EXTENDED PROCESSING LATITUDE FROMA FOAMABLE PRECURSOR COMPOSITION WHICH INCLUDES AS STABILIZING AGENT AN EFFECTIVE AMOUNT OF A COMPOSITION COMPRISING THE REACTION PRODUCT, HAVING AN INTRINSIC VUSCOSITY, (N) IN DECLITERS PER GRAM, DETERMINED IN CHLOROFORM AT 30*C., OF LESS THAN ABOUT 0.35, OF THE POLYMERIZATION OF THE MONOMERIC ESTERS OF MERTHACRYLIC ACID AND ALCHOLS HAVING FROM 3 TO 5 CARBON ATOMS, EFFECTED IN THE PRESENCE OF CHAIN TRANSFER AGENTS.

nited States Patent 3,824,204 STABILIZATION OF VINYL RESIN FOAM SYSTEMSElwood E. Huntzinger, Springfield, and Nelson N. Schwartz, Broomall,Pa., assignors to Air Products and Chemicals, Inc., Philadelphia, Pa. NoDrawing. Filed June 2, 1971, Ser. No. 149,325 Int. Cl. C08f 45/28 US.Cl. 260-291 R 1 Claim ABSTRACT OF THE DISCLOSURE Vinyl resin foamproducts having desirable characteristics including fine uniformcellular structure and low density are prepared with extended processinglatitude from a foamable precursor composition which includes asstabilizing agent an effective amount of a composition comprising thereaction product, having an intrinsic viscosity, [97], in deciliters pergram, determined in cholroform at 30 C., of less than about 0.35, of thepolymerization of the monomeric esters of methacrylic acid and alcoholshaving from 3 to 5 carbon atoms, effected in the presence of chaintransfer agents.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionconcerns the stabilization of vinyl resin foam systems to providecellular or porous resinous bodies.

2. Prior Art Vinyl plastics of the type generally known as polyvinylchloride or PVC constitute a large segment of the plastics art. Thepreparation and use of foamed polyvinyl chloride falls within a fairlynarrow area of the vinyl plastics art. Typical general prior art appearsin such US. Patents as 2,056,796; 2,960,728; 3,093,525; 3,050,412;3,063,110; 3,197,472; 3,267,197; 3,270,032; and 3,284,- 545. Moreclosely related are US. 3,399,107 and US. 3,417,038 of which 3,399,107concerns the use of homopolymeric methacrylate esters in relatively highconcentrations in the preparation of certain cellular polyvinyl chlorideproducts.

The present invention brings to the art an effective and economicalstabilizing agent capable of providing foamed polyvinyl chloride andpolyvinyl chloride products not only with improvements in theirformation but also with improvements in the product such as have beenpreviously unattainable with the ease and consistency now made possible.

SUMMARY OF THE INVENTION This invention concerns the stabilization ofpolyvinylchloride plastic compositions, having foamed cellularstructures during their formation and transformation to final form. Theprecursor plastic comopsitions comprise a vinyl resin and a plasticizingagent. Provision for the creation of the foam or cellular structure isgenerally made by inclusion in the precursor composition of a blowingagent which may, however, be reduced in amount or eliminated entirely bymechanical, i.e., froth, technique in creation of the foamed or cellularstructure. Stabilization of the foam, along with other improvementsdescribed herein below, is obtained when there is present with theprecursor materials during the foaming and fusion step or steps anamount in the range of 0.05 to 2.0 part by weight based on the polymericmaterial as herein defined per 100 parts by weight of fusible resin inthe formulation a polymeric material having an intrinsic viscosity [7 30CHCl in the range of 0.05 to 0.35 and obtained as 3,824,204 PatentedJuly 16, 1974 in which M is the molecular weight, k and on areconstants, and a is between 0.5 and 1. Thus the higher the intrinsicviscosity of a polymer, the higher the molecular weight.

The polymeric material stabilizer additive of this invention may beprepared by any method whereby a pre ponderant amount of the monomericmethacrylate and a minor amount of chain transfer agent react to formpolymeric product having an intrinsic viscosity [1 30 CHCl in the rangeof 0.05 to 0.35 upon suitable polymerization initiation and atacceptable polymerization conditions. Such polymeric material may berecovered in substantially pure form from the polymerization system byknown means which include precipitation of the polymer with anon-solvent, solvent evaporation, filtration or the like. Preferablyhowever the reaction product is obtained at conditions and in suchsystems such that the entire solution is recovered and employed asrecovered and used in amounts providing the polymeric material in theabove-defined range.

The monomeric C to C methacrylates are appreciably more suited to thepreparation of the polymeric materials than the methacrylate esters ofthe ethyl or lower alcohols or of the hexyl or higher alcohols. Thenormal butyl methacrylate and the isobutyl methacrylates areparticularly desirable.

The chain transfer agents include the known chain transfer agents suchas mercaptans, halo compounds such as carbon tetrabromide or carbontetrachloride, compounds with allylic hydrogen, or the like which act inknown manner in the non-interference with the kinetic chain which actswith the aid of the transfer reaction to produce several polymer chains.While it is not surprising that the chain transfer agent usage here hasthe result under the appropriate conditions of providing the polymericmaterial product in the relatively shorter polymer chain lengths asindicated by the lower values of intrinsic viscosity, it was discoveredthat the polymeric materials thus obtained are surprisingly moreeffective than the high molecular weight homopolymers derived fromsimilar monomeric methacrylates in some somewhat related use systems anddistinctively different in other systems not too otherwise dissimilar.

A particularly surprising result was discovered in finding that certaincompounds having: vinylic H, particularly dibutyl maleate and dibutylfumarate, are particularly effective in the role of transfer agents ingiving an effective polymeric material of excellent stabilizing natureeither as the polymeric material itself or more particularly when theentire polymerization system is such as to permit its use in itsentirety as recovered.

It is, therefore, among the objects of this invention to (a) to providea polyvinyl resin foamed product of desirable nature including fine porestructure, with the pores uniformly sized and distributed throughout thestructure;

(b) to provide increased tolerance in the ability of emulsion gradeplastic resin to accommodate extender (suspension) grade resin and stillproduce quality product;

('c) "to provide greater processing latitude in times and temperaturesin the preparation of products, particularly at unsually high fusiontemperatures previously considered detrimental to the production ofquality product;

(d) to increase the capacity of precursor formulations for higher fillerloading and for greater pigmentation;

(e) to provide precursor formulations amenable to ready processing byinjection molding and by calendering; and

(f) to provideenhanced manipulative techniques through utilization ofproperties associated with and in accordance with the products andprocesses of the invention.

These and other related objects will be apparent from the detaileddescription and examples which follow. While the following materialdescribes a preferred mode of operation and various typical embodiments,it is understood that the presentation is of an instructive andillustrative nature.

DETAILED DESCRIPTION OF THE INVENTION As noted above the chain transfercontrolled polymerization of the C -C methacrylate may be effected inany appropriate manner. The practical system is typically one involvinga solvent characterized in its ability to dissolve the precursors andproduct and is employed in an amount ranging from the minimum requiredfor such solvation to a maximum limited, more for practical reasons thanfor effect on the reaction, to about 2 times by weight of the weight ofthe C -C methacrylate involved. Such solvent is further required to benonreactive in the precursor composition in the absence of a suitablepolymerization initiator although the solvent may be reactive in thepresence of an initiator and may of itself have chain transferproperties. Such a solvent must be compatible with all of theingredients as well as with the end use systems when its presence isretained in part or in toto in the polyvinyl chloride foamstabilization. Such solvents, therefore, include mineral spirits,benzene, toluene, xylenes, carbon tetrachloride, chloroform,bis-(2-ethyl-hexyl)phthalate, and related materials known and/ordetermined as suitable.

The polymerization reaction requires the use of an initiator to startthe chain formation. Such initiator may be any of the free radical type,of which the various peroxides are embodiments. Benzoyl peroxide is onesuch suitable initiator. The initiator use requires a measure of care inthat it is known excessive amounts may lead to un desirable and possiblyviolent reactions. Also to be noted is that chain length and thusmolecular weight of the polymeric product is sensitive, in addition tothe polymerization temperature and the amount and type of chain transferagent, to the amount of initiator employed and that the chain lengthdecreases inversely with regard to the amount of initiator in thesystem. To all practical purposes therefore to obtain proper reactioninitiation, polymer chain length within the prescribed range and forsuitable reaction control the initiator usage level is within the rangeof 0.1 to 5.0% by weight of the weight of the C -C methacrylate in thepolymerization system exclusive of other ingredients such as thesolvent.

Thus, typical polymerization precursor systems have 30-50% of the C -Cmethacrylate monomer, 0.2-5.0% initiator, chain transfer agent of atleast 0.5% and up to 20% when the chain transfer agent and the solventare different and the solvent is not a chain transfer agent and up toabout 69% when the solvent is a chain transfer agent.

Of the various methods for the polymerization reaction anunsophisticated method is to have all the ingredients in a reaction zonein an inert atmosphere, e.g., nitrogen, and to effect the reaction byheating the contents at a temperature in the range of 70-100 C. for atime period in the range of about 3 to 8 hours at about atmosphericpressure with continuous agitation. Exclusive 0f the above-noted eflfectof the initiator on molecular weight, the molecular weight tends to belower at higher temperature.

Another somewhat more sophisticated but fundamentally similar systeminvolves charging the reactor vessel with a portion of the solvent andthe monomer with or without a portion of the initiator and/or chaintransfer agent or neither and under a nitrogen cover heating to atemperature of 70100 C. with stirring. To the reaction zone there isthen added simultaneously at a more or less uniform rate over a periodof 2 to 8 hours a first solution comprising a mixture comprising thebalance of the monomer and transfer agent; and a second solutioncomprising the balance of the solvent and initiator. For uniformity ofproduct it may be found desirable to maintain the reactant mass at theelevated temperature with continued stirring for an additional periodsuch as 30 to minutes after all of the ingredients have been combined.

Consideration of the following examples will aid in an understanding ofprocedures and advantages available in accordance with this invention.

EXAMPLE I A polymeric composition was prepared from a system comprisingisobutyl methacrylate and dibutyl maleate. The preparation was asfollows:

To a glass lined vessel was charged Parts by Weight Isobutylmethacrylate 4.6 Dibutyl maleate 6.9 Mineral spirits 11.5 Dibenzoylperoxide 0.06

The vessel was swept with nitrogen and a slight positive flow ofnitrogen was thereafter maintained throughout the reaction period. Thecontents of the vessel were stirred and heated to 90 C., whichtemperature was held substantially constant during the subsequentreaction period.

The polymerization reaction was continued by maintaining the contents ofthe vessel at 90 C. for 30 minutes after all solutions were charged tothe vessel.

The contents of the vessel were then cooled to about room temperatureand recovered. The recovered material was a colorless liquid with aBrook-field Viscosity at room temperature of 650 cps. The NMRspectrographic examination of the product indicated that somewhat morethan of the isobutyl methacrylate had polymerized (showed less than 5%isobutyl methacrylate of the original charge); also, that somewhat lessthan 5% of the original dibutyl maleate was no longer present as thefree maleate. l

A portion of the product was treated with methanol to precipitate thepolymeric material which was separated and recovered. This recoveredmaterial was purified by dissolving in acetone, treated with water toagain precipitate the polymeric material, and the precipitate wasseparated and dried. From the dried sample a portion was dissolved inCHCl and the intrinsic viscosity [1 was determined at 30 C. as being0.247. The weight average molecular weight was 55,000 and the numberaverage molecular weight was 30,000 as determined by gel permeationchromatography. The NMR and IR spectra were similar to those ofhomopolymeric isobutyl methacrylate, being unable to distinguish thestructural difference in the overwhelming or smothering situation of thepredominantly methacrylate polymer structure.

A formulation was prepared using the following:

Ingredient: Parts by Weight PVC resin (Geon 124) 100 DIOP (di-isooctylphthalate) 60 BBP (butyl benzyl phthalate) 20 Epoxidized soybean oil(Paraplex G-62) 5 Heat Stabilizer (Advastab ABC7) (Ba-Cd-Zn) 3 BlowingAgent (Kempore 125) (Azodicarbonamide 3 This plastisol formulation wasemployed in foam formation without cell stabilizer additive and withvarying amounts of the cell stabilizer product prepared as describedabove. The several samples without and with added cell stabilizer werespread as a 25 mil coating on release paper and fused and expanded for 1/2 minutes at 460 F. Product of the material Without the cell stabilizerhad a rough surface and had approximately 30 cells per linear inch, acndition unsatisfactory and unacceptable as suitable foam product whichgenerally requires a cell count per linear inch of at least 120. Theproduct of the material containing the cell stabilizer added on thebasis of the solids concentration in the recovered product of amounts of0.2, 0.4, 1.0 and 2.0 parts per 100 parts of the resin had smoothsurfaces and cell counts in every case above 170 cells per linear inch.The foam product of the plastisol containing the cell stabilizer hadexcellent physical and mechanical properties including foam densities inthe order of 20 lb./cu. ft.

In the same formulation polymeric products prepared from isobutylmethacrylate having intrinsic viscosities of 0.56 and 1.13 respectively,when formulated and fused in like manner at like concentrations, gaveproducts of generally poor and unacceptable quality in both surfacecharacteristics and low cell counts.

EXAMPLE II A readily foamable recipe was prepared to illustrate theimprovement obtainable in resistance to overblowing."

Parts by Weight In the absence of added cell stabilizer this materialwhen fused at 460 F. for 3 /2 minutes resulted in a collapsed foamsystem having rough and irregular distribution of the pores of 30*50 perlinear inch. However, when the cell stabilizer of Example I was added tothe above formulation in amounts ranging from 0.1 to 1.5 parts by weightbased on the weight of contained solids per 100 parts by weight of theresin, the products had excellent and uniform pore sizes anddistributions ranging in the order of 200 cells per linear inch anddensities in the ranges of 18 to 20 lb./cu. ft. In similar runs wherethe cell stabilizer product of Example I was diluted with added mineralspirits to a level of contained solids of 25% by weight, equally goodresults were obtained when used in the formulation in the same range ofconcentration based on weight of contained solids.

A further advantage resides in the use of the cell stabilizer withsimilar formulations employed in the production of foam covered fabricswhich are prepared by first coating the fabric with plastisol, causingthe plastisol to foam and fuse and then in a second operation furthersubjecting the thus coated fabric to heat embossing. Here, the use ofthe cell stabilizer additive in amounts such as in the order of 0.1 to0.5 parts by weight per 100 parts of resin reduces to a considerableextent the temperature criticality heretofore normally existing in theprevention of foam collapse during the heat embossing period. Thepractical temperature range would thus be extended from a range of about10 F. to a broader range of about 50 F. or greater.

In the same formulation the effectiveness of the cell stabilizer asprepared in Example I on the foam stabilization efficiency over extendedtime periods is shown in Table 1 below.

tisol grade resin to the presence of increased amounts of lower costextender or blending grade resin is shown in connection with a plastisolformulation generally similar to that shown in Example I with theexception that the resin composition was as shown in Table 2 whichlikewise shows the amount of cell stabilizer employed and the effect onfoam quality. The test samples were prepared by forming a 30 mil wetplastisol coating on release paper and foaming and fusing for 2 minutesat 440 F.

TABLE 2 Cell stabilizer of PVC resin (percent) Example I Pliovic QYKV(extender Foam (dispersion resin) quality, resin) M- Phr. cells/inch Theabove table shows the presence of the cell stabilizer has a highlybeneficial effect at high level usage of extender resin in theformulation.

EXAMPLE IV A formulation was prepared as follows:

Geon 124 (Paste PVC Resin) 60 Escambia 8200 (Extender PVC Resin) 40 DOP(di-(Z-ethyl-hexyl) phthalate) 80 Dythal (dibasic lead phthalate) 3Calcium carbonate as shown Azodicarbonamide 2 Cell stabilizer as shownVarious amounts of calcium carbonate filler were employed and samplesystems without and with the cell stabilizer are shown in Table 3 below.

TABLE 3 Cell stabilizer of Ex- Foam ample I, quality, phr. cells/inchThe above data show that the use of as little as 20 parts per parts byweight of resin of calcium carbonate filler in the absence of the cellstabilizer results in foam collapse to an unacceptable product. On theother hand with cell stabilizer present acceptable product is obtainedwhen as high as 60 parts by weight per 100 parts by weight of resin ofcalcium carbonate filler are present.

EXAMPLE V In the preparation of colored products comprising polyvinylchloride, the matter of pigmentation is extremely important to theproducer. As shown below the use of the cell stabilizer in thisinvention substantially enhances the ability of polyvinyl chloridesystems to tolerate a high order of pigment additive and thereby obtaina desirable richer coloration. A formulation was prepared as follows:

Marvinol 53 (dispersion resin) 70 Marvinol 14 (blending resin) 30 DOP 20DIDP (diisodecyl phthalate) l8 Monoplex NODA (n-octyl n-decyl adipate) 9Admix 711 (epoxidized oil) Vanstay 8300 (Pb stabilizer) 1.9 Ferro 5078(Pb stabilizer) 0.1 Atomite (calcium carbonate) l5 Azodicarbonamide 1.8Carbon black pigment as shown Foam stabilizer as shown The samples wereprepared as cast films and foamed and fused for 4 minutes at 420 F.Comparative data are shown in Table 4. These data show that quality foamproduct was obtained at carbon black pigmentation loading levels twiceas great by the use of the cell stabilizer as in the absence thereof.

Advantages of the use of the cell stabilizer of this invention are notlimited to free rise PVC foam systems as may be determined in thisexample concerning a molded foam product of the type utilized in thepreparation of soles for shoes. A formulation was prepared as follows:

V0 100 PM (Injection molding grade of PVC) 100 DOP(bis-(Z-ethylhexyl)-phthalate) 73 Paraplex G-62 (epoxidized oil) 8Actafoam R-3 (commercial heat stabilizer and blowing agent activator) 2Stearic acid 0.15 Atomite (calcium carbonate) 8 Azodicarbonamide(blowing agent) 0.75 Foam Stabilizer (of Example I) as shown The aboveformulations in the various lots as indicated below were separatelymixed in a Hobart mixer at low speeds for aproximately minutes. Eachmixture was fluxed on a 2 roll mill at roll temperatures in the order of270-300 F. for 7 minutes. The milled product was sheeted off at 0.25"thickness. A suitable mold and unattached cover plate was preheated in asteam heated press at 360 F. for at least minutes and then filled withthe cut strip having dimensions of approximately 4" x 1". The coverplate was applied and fastened. Pressure in the press was adjusted at5000 p.s.i.g. and the mold was maintained at about 360 F. and 5000p.s.i.g. for 6 minutes. Pressure was released to allow for expansion ofthe stock and cooling by means of a water flow was effectedsimultaneously. After approximately 2 minutes the mold assembly wasremoved from the press and final cooling was effected by immersion intap water. After the specimens were cooled they were removed from themold and the products had characteristics shown as in Table 5.

TABLE 5 Foam Cell stabilizer of Exquality, Blow ample I (phr.)cells/inch ratio 1 1 Ratio of final foam thickness to unblown stockthickness.

EXAMPLE VII Calendered foam products likewise can be improved when thecell stabilizer of this invention is employed. A recipe was prepared asfollows:

Vygen (calendering grade of PVC) 100 DIOP (diisooctyl phthalate) 80Nuostabe V-l026 (Pb stabilizer) 2 Stearic acid 0.4 Azodicarbonamide(blowing agent) 5 Foam Stabilizer as shown The ingredients were handmixed and then fiuxed on a 2 roll mill at 260-280 F. for 7 minutes andthen removed from the mill by sheeting oflf at 30 mils thickness. Thesheets were cut into 2" x 2" pieces, placed on release paper, and foamedand fused in a mechanical convection oven at 440 F. for 2.5 minutes. Theresults are shown in Table 6 below.

TABLE 6 Minimum Effective Foam Stabilizer: Concentration, phr. Accordingto US. 3,270,032 0.45 Of Example I 0.20

1 Quantity of foam stabilizer needed to produce a foam having a cellcount of to cells/inch. In the absence of a cell stabilizer cell countsare in the 25 to 50 cells/inch range.

EXAMPLE VIII In a manipulative manner idicated with that shown for thepreparation of the cell stabilizer material of Example I, the reactionvessel was charged with Parts by Weight Isobutyl methacrylate 4.6Dibutyl fumarate 6.9 Mineral spirits 11.5 Dibenzoyl peroxide 0.06n-Dodecyl mercaptan 0.06

T 0 this was added the 2 separate solutions, one composed of 69 parts byweight of mineral spirits and 0.6 part by weight of dibenzoyl peroxide;and the second solution composed of Parts by Weight Isobutylmethacrylate 69.1

Dibutyl fumarate 4.6 Mineral spirits 4.6 n-Dodecyl mercaptan 0.6

The product recovered from this reaction, except for a mild butnoticeably different odor, had physical and chemical properties similarto the cell stabilizer product of Example I. When employed as cellstabilizer in like amounts in identical formulations the stabilizingactivity in all instances was at least as effective as the demonstratedeffectiveness of the cell stabilizer of Example I.

EXAMPLE IX The procedure of Example I was followed in the preparation ofcell stabilizer except that normal butyl methacrylate was substitutedfor isobutyl methacrylate. The polymeric material in the product had anintrinsic viscosity of 0.23 and was approximately similar in its cellstabilizing and other beneficial aspects to that of the product of thepolymerization reaction in Example I.

9 EXAMPLE X In a polymerization run similar to that in Example I exceptthat dilauroyl peroxide was used as initiator and no chain transferagent was employed, the polymer after polymerization reaction at 80 C.had an intrinsic viscosity of above 0.4 and the recovered product wasgenerally ineffective as a cell stabilizer in the formulation of Example1.

EXAMPLE XI Following the procedure of Example I similar ingredients wereemployed in the same amounts with the exception that xylene wassubstituted for the mineral spirits, and the chain transfer agent waschanged from dibutyl maleate to 0.7 parts by weight of dodecylmercaptan. Xylene does exhibit some chain transfer properties. Theisolated polymer from the recovered product had an intrinsic viscosity,[1;], of about 0.31. The total product composition in tests of its cellstabilizing effectiveness showed an effective minimum concentration toproduce a cell count above 120 cells per linear inch in the plastisolformulation of Example I to be in the order of 0.6 part by weight per100 parts of resin.

EXAMPLES x11, XIII, AND Xrv The halogen compound used in Example XII wasdissolved in the monomer, while that used in Examples XIII and XIV wasadded to a 500 mil reaction flask. A volume of solvent equal to that ofthe monomer and halogen compound dissolved therein was used to dissolvethe peroxide, and the remainder of the solvent was placed in thereaction flask. The monomer and solvent solution were then addedsimultaneously at constant rates over 6 hours to the stirred flask, thecontents of which were maintained under nitrogen at 80 C. throughout theaddition period, and for /2 hour longer. The solutions were then cooled.

The materials recovered from the several reactions had polymericproducts, as measured on separated polymer solids, with intrinsicviscosity values of less than 0.3. The recovered products, unseparated,employed as cell stabilizers in the plastisol formulation of Example I,each exhibited an effective minimum concentration to obtain cellstructured product of above 120 cells per linear inch in the range of0.4 to 0.5 part by weight per 100 parts by weight of resin.

EXAMPLE XV Two separate batch polymerization reactions were run, eachemploying 14.2 parts by weight of isobutyl methacrylate dissolved in 30parts by weight benzene and differing in that one contained 0.2 part byweight dibenzoyl peroxide and 0.1 part by weight of n-dodecyl mercaptanand the other contained 0.1 part by weight of dibenzoyl peroxide. Eachbatch was stirred at reflux condition under nitrogen atmosphere for 4hours. The polymeric material in the product from the batch containingthe mercaptan had an intrinsic viscosity of 0.17. The product from thebatch containing no mercaptan but also considerably larger than normalamount of initiator had an intrinsic viscosity of 0.30, indicative ofthe possibility of obtaining relatively low molecular weight product ina system with the chain length shortening effect of a relatively largeamount of initiator. In tests on cell stabilizing activity, the sampleprepared with the mercaptan showed an appreciably higher foamstabilizing activity than the higher molecular weight material preparedin the absence of mercaptan. The minimum effective concentration toobtain foamed product from the resin formulation of Example I to producea cell 10 structure above 120 cells per linear inch was 0.3 for thematerial prepared with mercaptan as opposed to 0.7 part by weight perparts of resin of product prepared in the absence of mercaptan.

The foregoing description has concerned polyvinyl chloride resins andresinous compositions as embodiments of the materials favorablyresponsive to the stabilizing effect of the stabilizers of theinvention. It is to be understood that such descriptive terminologyincludes those copolymers which are derived from predominantly vinylchloride with minor amounts of copolymerizable comonomers. For instancethe cell stabilizer material of this invention is very effective instabilizing the relatively loW- temperature fused foam carpet backingderived from copolymers of polyvinyl chloride and polyvinyl acetate.

Other tests have demonstrated that the cell stabilizer of the inventionprovides a marked advance in processing and preparation of qualitycellular products Where arbnormally high processing temperatures areencountered or desired. This feature is highly desirable in that ovenresidence time can be reduced substantially with a resultant increase ofproduction rate. It has been found that with the cell stabilizer of theinvention temperatures as high as 535 F. are feasible for times up to0.7 minutes and that temperatures up to 550 F. are possible for times aslong as 0.5 minutes.

Obviously, many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof, and therefore only such limitations should be imposed asare indicated in the appended claim.

What is claimed is:

1. A cell stabilizer for use in forming foamed polyvinyl chlorideplastic compositions which have at least fine and uniformly distributedcells per linear inch, said stabilizer consisting of the total productof the reaction, at polymerization conditions, of a precursorcomposition of at least one monomeric methacrylate ester of methacrylicacid with a C to C alcohol; a chain transfer agent selected from thegroup consisting of dibutyl maleate and dibutyl fumarate; an initiator;and solvent, said solvent being present in an amount at least sufficientfor solvation of precursors and product to an amount equal to and nogreater than 2 times the weight of monomeric methacrylate ester, andsaid solvent being non-reactive in the precursor composition, in theabsence of said initiator, wherein said precursor composition consistsof 0.1 to 20 parts by Weight of chain transfer agent and 0.05 to 2.0parts by weight of initiator per 100 parts by weight of the monomermethacrylate ester, and wherein the separable polymeric materialproduced from said total prodnot of reaction has an intrinsic viscosity,measured at 30 C. in CHCl in the range of 0.5 to 0.35 deciliters pergram.

References Cited UNITED STATES PATENTS 2,204,517 6/1940 Strain 260-895 A2,534,108 12/1950 Johannes de Nie 260--78.5 E 2,598,639 5/1952 Fields eta1. 260-89.5 A 2,752,387 6/1956 Rehberg 260-895 A 2,047,398 7/1936 Vosset al 260-78.5 E 2,396,997 3/1946 Fryling 260-78.5 E 2,740,772 3/1956Alfrey 260-.86.1 E

OTHER REFERENCES Monomeric Acrylic Esters, Edward H. Riddle, Rohm & HaasCo., Reinhold Pub. Corp., 1954, New York, pp. 56-58.

ALLAN LIEBERMAN, Primary Examiner J. H. DERRINGTON, Assistant ExaminerUS. Cl. X.R.

260-2.5 P, 31.8 R, 33.6 UA, 33.8 UA, 78.5 E, 89.5 A

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTIONPATENT NO. 1 4 DATED July 16, 1 974 INVENT Elwood E. Huntzinger andNelson N. Schwartz It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

I N THI; CLAIMS:

Column 10, Line 53, after the phrase, "in the range of", delete "0.5",and insert 0.05-

En'gncd and Scaled this Thirtieth D3) 0f May 1978 |st1.-'\|.|

.1 trust:

RL'IH \IASUN LUIRELHI F. PARKER Amxting ()jlir'er Arring ('ummixsinnerof Patenls and Trademark;

